Brake operating mechanism for use with trailers



Sept. 3, 1935. 2,013,033

OPERATIN MECHNISM FOR USE WITH TRAILHERS l C. V. CLARKE BRAKE Filedv Nov, 22, 19:55v

3 Sheets-Sheet l Spt. 3, 1935.

C. V. CLARKE BRAKE OPERATING MECHANISMFOR USE WITH TRAILERS` Filed Nqv; 22, 193s :s sheets-sheet 2 34 55 g-7W v 5.9

y f5 93' y.92 95 l-lllllmmiqJ fl 59/ 39 1&2 8g v' W f vwf'ef Sept. 3, 1935.

BRAKE OPERATING MECHANISM FOR USE WITH TRAILERS Filed Nov. 22, 19:5

c. v. CLARKE 2,013,033

5 Sheets-Shet 3 iii: y M

amarte MMM ' Hmm @lt'lEli'ti'llfllNG MECHANHSM 'FR USE WlITllHl 'IFRIMMERS Cecil Wandepeer illlarlre, Bedford, England Application November 22, 51933, Serial No. 699,283 lin Great Britain November 29, i932 n comme. (ci. isa- 3) This invention relates to brake operating mechanism for use with trailers.

The invention is illustrated in the accompanying drawmgs in which Figure 1 is a section partly in elevation and Figure 2 a sectionalview to a larger scale of part of the mechanism shown in Figure l, Figure 3 a sectional view of a modified arrangement, Figure 4 a general view showing the apparatus according to the invention applied to towing and towed vehicles and Figure 5 a Wiring diagram. Figure 6 is a detail View showing a fluid motor operated brake on an enlarged scale.

Referring rstly to Figure 4, which shows in diagrammatic form the application pf the invention, A is a towing vehicle and B a towed vehicle connected through a draw bar 35 to the towing vehicle A, the draw bar being placed in operative connection with the towed vehicle B through a ram and cylinder mechanism denod generally by C now to be described.

Referring now to Figures 1 and 2, the draw bar 35 is connected to a ram :it working in a cylinder 3l secured to the towed vehicle B, the draw bar being formed with three diameters 351, 352, 353 of which the largest diameter part is formed with an eye, the intermediate part with a screw thread, and the smallest part connected to the ram Siti. 38 is an automatic non-return valve which permits oil i or other fluid) to pass from a reservoir 39 through a passage 331 and a passage .W2 and into the right hand end of the cylinder when the draw bar and hence the ram are moved to the left as seen in the drawings, this movement occurring when the towing vehicle A accelerates with respect to the towed vehicle. The draw bar is provided with a sleeve l which is screwed on to the' threaded part 352 of the draw bar and has a ange il engaging a flange l2 on a sleeve dit having ears or flanges lil which slide on guide rods t5 secured to a bracket d5 carried by any convenient fixed part of the towed vehicle B. Between this bracket llt. and the ears or anges M are interposed springs tll and it will be seen that by reason of the anges All and l2 the movement of the draw bar due to acceleration will cause these springs il to be loaded.

As soon as the movement of the draw bar ceases, which occurs when the loading of the springs itl equalizes the tractive load, the valve 3d closes and oil drawn into the cylinder is trapped and thus prevents reverse movementof the draw bar 35. and the springs ll are held loaded by the trapped oil. Between the flange t! and a flange i3 formed on the sleeve 33 there is interposed a spring 3Q for a reason hereinafter referred to.

A second valve 5t arranged for manual operation is provided whereby the trapped oil can be allowed to escape from the right hand end of the cylinder. This valve normally closes a passage El in communication with the right hand end of the cylinder 3l, and provides a double closure; one closure is formed by the end peripheral portion of the valve t@ which directly seals the passage 5l and the other closure is provided by boring and bevelling the end face of the valve and arranging for the sharp ridge thus formed to co operate with a valve seating 52 for a central aperture 53. When the valve is moved to the open position (in which position it is shown in the drawing) communication is established between the aperture t3 and the passage 5l and thus oil is allowed to escape to the reservoir 35i.

A similar arrangement of valves is employed for the left hand end of the cylinder 3l, the ram 3&5 thus being double acting; thus the left hand end of the cylinder is provided with a spring loaded inlet non-return valve (il which allows oil to be drawn from the reservoir 3Q through a passage til and a passage M2 into the left hand end of the cylinder when the ram moves to the rightdue to decelerationof the towing vehicle A with respect to the towed vehicle B, and trapping this oil when lthis movement of the ram ceases; this end ofthe cylinder is also provided with a passage 62 arranged to be opened and closed to the reservoir by a manually operable valve ii similar to the valve 53 operating to provide a double closure, there being provided a valve seating member GE, this valve t5 enabling the oil trapped in the left hand end of the cylinder to escape. The outlet valves for both ends of the double acting ram and cylinder arrangement are arranged for simultaneous but reverse operation so that when one is opened the other is closed; to effect this the valvesv are formed as a single piston valve so that when the valve moves to close one passage 5l it opens the other passage @2. It will now be seen that when the valve iii?, t5 is operated to open the passage li?, the draw bar can move to the left but is prevented from reversing (i. e. moving to the right) as long as the valve remains in this position; when, however, the valve 5d, @d is reversed (i. e. moved tothe position shown in the drawing) to open the passage 5l the draw bar can move. to the right but is prevented from reversing (i. e. moving to the left) until the valve Fill, titi is again moved to the right. These movements of the draw bar are utilized to eiect operation of the brakes on the towed vehicle and for this purpose the sleeve it is associated with brake operating mechanism in the manner hereinafter referred to; the association is such that movement when permitted of the draw bar to the left (corresponding to acceleration of the towing vehicle A with respect to the towed vehicle B) effects release of the brakes which are held released until the draw bar is permitted to reverse; when this reverse is permitted the brakes are applied with the assistance of the springs 41 and are held applied despite traction applied through the draw bar until the draw bar is again permitted to move to the left, the brake actuating operation thus being under the control of the valve 50, 65.

The valve G, 65 is arranged for manual control from the towing vehicle and it is preferred that transmission for effecting valve actuation shall be effected electricallyfor the reason that operative connection can readily be established between the operating and operative parts on the towing and towed vehicles respectively. This is effected by the provision of a solenoid 55 which is varranged to be energized by a switch 8l on the towing vehicle and the armature 56 of which is slotted or grooved to receive a lever 51 pivotally mounted at 58 and connected by a pin 59 to the l valve 50, 65l the armature being biased by a spring 60 to move into a position corresponding to the closure of the passage 5|. It will be seen that when the switch 8l lon the towing vehicle is closed to energize the solenoid, the armature thereof is moved to the left (into the position shown) and the valve 50, 65 is operated to allow the escape of oil from the right hand end of the cylinder and thus to permit the reapplication of the brakes on the towed vehicle.

The additional spring 49 transmits an additional braking force when very rapid retardation of the towing vehicle occurs or when the towing vehicle is held on an up-gradient by the brakes of the towed vehiclel For example, if the brakes of the towing vehicle completely fail, by changing into a lower gear without acceleration of the engine, a sudden momentary retardation can be obtained, and the resulting momentary over-running force will increase the force of application of the trailer brakes, and if the latter are of ample proportions, will ensure that both vehicles are brought to a rest in a reasonable distance.

It is preferred to provide a definite limit to the braking effort and this is effected by providing the end of the draw bar 35 with a cap 354 of resilient material and adapted to abut against the end wall of the cylinder thus resiliently checkingv the movement of the draw bar.

The mechanism previously described is associated with the brakes of the towed vehicle, (the brake shoes and brake drum being indicated at 83, 831 in Figure 4), through an hydraulic braking system in which a master hydraulic ram and cylinder arrangement is arranged to be moved and to transmit an impulse through a liquid in pipe line 84 to a spring or otherwise biased ram and cylinder arrangements 85 in operative connection with the brakes 83. To effect this the master'ram and cylinder is incorporated as an .e

integral part of the structure of the control system, this arrangement being carried into effect as follows: there isprovided a second ram 61 and cylinder 68 the ram being in the form of a sleeve surrounding the draw bar and being screw threaded at its outer end to the sleeve 43. In its simplest form, the ram and cylinder arrangement i is such that a connection between the annular cylinder 68 and the reservoir 39 is established by a passage 69 which is opened by the second ram 61 when the 4draw bar is at or near the end of its movement due to acceleration f the vehicle A with respect to the vehicle B: this second cylinder is provided with a spring loaded outlet valve which when the piston valve 55 is opened to effect application of the brake is opened by the fluid pressure created in thesecond cylinder 68 by the second ram 61 and this pressure is transmitted through the fluid in the pipe line 84 to the brake operating cylinder and ram arrangements B5 to effect application of the brakes 83. A second spring vloaded valve 161 concentric with the valve 10 is also provided, this second valve being caused to open by the drop in pressure created by the movement of the second ram 61 when the draw bar is permitted to move to release the brake; this allows liquid to return to the cylinder 68 of the master ram; any deficiency or excess in the quantity of liquid contained in the system between the master and operating ram or rams is made good by the opening of the passage 69.

When an hydraulic system is employed in connection with large towed vehicles (for example 8-10 ton trailers) a considerable quantity of oil (or other fluid) has to be displaced into the cylinders containing the brake operating rams, while at the same time a high pressure has to be exerted: these effects have to be obtained from a comparatively short stroke of the master ram and to achieve this the modification shown in Figure 3 is employed. The parts in the arrangement shown in Figure 3 which correspond to the parts in the arrangement shown in Figures l and 2 are for convenience in understanding the modication given similar reference numerals. It will be seen that firstly the passage 69 and the spring loaded outlet valve 10 and inlet valve 1!)l are dispensed with. Secondly the left hand end of the cylinder 31 is employed as a feed chamber for the master cylinder 68,4 oil being displaced by the ram 36 from the cylinder 31 to the cylinder of the master ram when the draw bar is moved to release the brakes. Thirdly, the greater part of the supply of oil to the system is effected by displacement from the right harid end of the cylinder 31. Thus, there is provided between the left hand end of the cylinder 31 and the right hand end of the master cylinder 63 a partition 1I in which slides a sleeve 12 secured to the master ram 61 so as to reduce the effective area thereof and to enable a high pressure to be developed. The partition is provided with apertures 13 covered by a resilient washer 14 functioning as a flap valve and the sleeve 12 is provided with passages 15 which, when the draw bar is at or near the end of its out-stroke are uncovered by an annular portion 16 of the washer 14 to place y the master cylinder into communication with the left hand end of the cylinder 31. The passage 62 is moreover, provided with a spring loaded non-.return valve 11 which determines the lowest value (which is preferably of about 10.1bs. per square inch) at which oil can return tothe reservoir; the valve selected is such as will operate to prevent or reduce the tendency of air from entering the system.

Moreover, the aperture 53 opens to a non-return valve 54 loaded to a pressure of say 50 lbs. per square inch and there `is provided a passage 18 which opens to the non-return valve 50 and also to a non-return valve 19 which is lightly spring loaded so as to close when the pressure inthe pipe line 84, to which the valve 19 is coninch.

nected by the connector til, rises above that determined by the valve tt.

When the ram dt moves onits forward strolre (i. e. to theleft as seen in the drawings the draw bar is moved to release the brakes) oil which had been drawn into the left hand end of the cylinder ill is forced through the apertures lli into the master cylinder bt. Excess oil (if any) is allowed to return to the reservoir past the valve 'il when the biasing pressure thereof is overcome, the excess oil which is. delivered to the master cylinder returning through the passages lb when uncovered by the part 'i6 of the washer it. lt will be understood that the ram fitta-nd draw bar d5 will be held by the oil trapped in the `right hand end of the cylinder di as has previously been described.

If now the solenoid be actuated so as to cause the valve tt to release the oil trapped in the right hand end of the cylinder di the rams tt, d'1, will be caused by the springs tl to move to the right and the oil in the right hand end of the cylinder di will be displaced through the now open valve tt and aperture 53, thence to the passage it and so to the pipe line of the system, the maximum pressure developed by this action is that determined by the valve tt (i. e. '50 lbs. per square inch) and this action is, sunicient to cause the brake operating ram to be displaced .so as to bring the brake shoes into contact with the drums with a pressure of 50 lbs. per square inch. dt they same time however, that the ram dt is creating this displacement and building up this pressure, the ram tl is also building up a pressure, so that the valve it is subjected to opposing pressures, one created by the ram dii and the other created by the ram lil. When .the pressure created by the ram til exceeds that created by the ram (which latter pressure cannot exceed the prese sure determined by the valve til), the valve it automatically closes and during the remainder of the stroke the ram tt discharges past the valve bd into the reservoir. The ram tl being oi small effective diameter and hence producing a high pressure intensity now transmits a high pressure through the oil to the bralre shoe operating rams to producethe final high pressure braking edect, this pressure may readily be produced up to a value of 1,000 lbs. per square lt will be apparent that the spring dit permits the ram fil to create an increased pressure under the conditions already referred to: it will also be understood that, as has previously been described oil drawn into the left hand end of the cylinder will be prevented from returning to the reservoir :it by the valve td and thus the bralres will remain applied until the solenoid is de-energized.

It may be noted that the valve tit when open permits oil to discharge to the reservoirI titi through a port tbl opening into an annular groove db2 which itself communicates with the slot through which the pin bt passes.

Electrical connection between the solenoid on the towed vehicle B and the switch di on the towing vehicle A is preferably effected by a plug and socket connector iltand conveniently there is employed a multiple-way plug and soclretA del vice, so as to feed not only the solenoid but also tail stop and reversing lamps on the towed vehicle, the casing for the lamps being indicated at tl inFigure 4. For this purpose there is employed a junction switch box di mounted on the solenoid casing and having. push-pull switches for controlli the lamp circuits and 'one of which is shown in Figure d at tid. A circuit diagram is shown in Figure 5 in which the stop, tail and reversingv lamps of the towed vehicle B are indicated .at de, tt and di, the push-pull switches for the tail and reversing lights at itl, dit, the stop lamp for the towing vehicle at td, and a feed battery titi. It will be seen from the diagram that when the switch di is closed, not only is the solenoid tb energized but also the stop lamps on the vehicles d and B. The armature tit or the solenoid may if desired have fast with it .a rod ttl which extends through the junction box lil and has an operating knob dd by means of which the rod B91 can be moved by hand (i. e., independently of electrical control) to edect application or release of the brakes by causing'movement of the valve tt, tt.

Preferably the switch controlling the solenoid is actuated against a light spring dt by the foot pedal till controlling the brakes on the towing vehicle, the spring insuring that the trailer brake is applied during the initial movement of the 'n foot pedal so that the brakes on the towed vehicle are applied before those on the towing vehicle, this arrangement thus providing a graduated degree of braking edort.'

The one or more brake operating ram and cylinder arrangements may be of any known hind and may for example each consist of a cylinder it@ having therein opposed rams iti between which the operating liquid is introduced and which abut at their outer ends against the brake shoes which are drawn towards one another by l a spring in the usual manner: thus, when the master ram is moved by reason of the movement produced on the draw bar by its spring the liquid displaced by the master rain eiiiects separation of the opposed rams and hence applies the brake shoes to the brake drum; when the master ram is moved in the reverse direction by reason oi' the movement of the draw bar due to acceleration, liquid is displaced from between the opposed rams which are caused to move towards one another by the spring acting on ,the brake shoes.

'lhis mechanism is well lznownv to those sed" in the art and therefore further description is believed to he unnecessary.

l.. lin bralre operating means for use on a vehicle towed by a towing vehicle, a device connecting the two vehicles while yetl petting relative movement between them, automatic means for'holding thevehicles against relative movement in both-directionsoperator operated means for rendering the holding means inoperative to permit selectively relative movement between the vehicles in one direction or the other,

brake operating means on the towed vehicle and iti ment between the vehicles in one direction or the other, brake operating means on the towed vehicle and means whereby the selective relative movement effects operation of the brake operating means, the relative movement in one direction effecting brake release operation and in the other direction effecting brake application.

l 3. In brake operating means for use on a vehicle towed by a towing vehicle, a device connectingthe two vehicles while yet permitting relative movement between them, fluid pressure means which operate automatically tohold the vehicles against relative movement in both directions, a first valve means for so relieving fluid pressure that relative movement between the vehicles is permitted in one direction, a second valve means for so relieving fluid pressure that relative movement between the vehicles is permitted in the other direction, operator operated means controlling the valve means so that as one is rendered operative the other is rendered inoperative so that relative movement between the vehicles is selectively permitted in one direction or the other,

brake operating means on the towed vehicle and means whereby the selective relative movement effects operation of the brake operating means, the/relative movement in one direction effecting brake release operation and in the other direction effecting brake application.

4. In brake operating means for use on a ve-i hicle towed by a towing vehicle, a double acting ram and cylinder arrangement one part of which` is operatively connected to one of the vehicles and the other part operatively connected to the other vehicle, a source of fluid supply, an automatic inlet valve for each side of the arrangement, an outlet valve for each side of the arrangement, opera-tor operated means controlling the outlet valves so that as one opens the other closes, the arrangement thus permitting the two parts of the arrangement to move relatively in one direction or the other by opening one of the outlet valves \and being prevented from reversing until the other outlet valve is opened whereby relative movement between the vehicles is selectively permitted in one direction or the other, brake operating means on the towed vehicle, means whereby the selective relative movement effects operation of the brake operating means, the relative movement in one direction effecting brake release operation and in the other direction effecting brake application, an energy storing device which is loaded by the relative movement causing brake release and in unloading assists the brake application operation.

5. Means as claimed in claim 4 and in which the two outlet valves are constituted by a single double acting valve member.

6. In brake operating means for use on a vehicle towed by a towing vehicle, a double acting ram and cylinder arrangement one part of which is operatively connected to one of the vehicles and the other part operatively connected to the other vehicle, a source of fluid supply, an automatic inlet valve for each side of the arrangement, an outlet valve for each side of the arrangement, electrically operated means controlling the outlet valves, an operator operated switch mechanism controlling the circuit of the electrically operated means so that asone outlet valve opens the other closes, the arrangement thus permitting the two parts of the arrangement to move relatively in one direction or the other by opening one of the outlet valves and being prevented from reversing until the other, outlet valve is opened whereby relative movement between the vehicles is selectively permitted in one direction or the other, brake operating means on the towed vehicle, means whereby the selective relative movement effects operation of the brake operating means, the relative movement in one direction effecting brake release operation and in the other direction effecting brake application, an energy storing device which is loaded by the relative movement causing brake release and in unloading assists the brake application operation.

7. In brake operating means for use on a vehicle towed by a towing vehicle, a device connecting the two vehicles while yet permitting relative movement between them, automatic means for holding the vehicles against relative movement in both directions, operator operated means for rendering the holding means inoperative to permit selectively relative movement between the vehicles in one direction or the other, brake operating means on the towed vehicle and an hydraulic transmission system whereby the selective relative movement effects operation of the brake operating means, the relative movement in one direction effecting brake release operation and in the other direction effecting brake application.

8. In brake operating means for use on a vehicle towed by a towing vehicle, a double acting ram and cylinder arrangement one part of which is operatively connected to one of the vehicles and the other part operatively 'connected to the other vehicle, a source of fluid supply, an automatic inlet valve for each side of the arrangement, an outlet valve for each side of the arrangement, operator operated means controlling the outlet 'valves so that as one opens the other closes, the arrangement thus permitting the two parts of the arrangement to move relatively in one direction or the other by opening one of `the outlet valves and being prevented from reversing until the other outlet valve is opened whereby relative movement between the vehicles is selectively permitted in one direction or the other, an hydraulic transmission system operating the brake operating means and itself operated by the selective relative movement to effect operation of the brake operating means, the relative movement in one direction effecting brake release operation and in the other direction effecting brake application 9. In brake operating means'for use on a Vchicle towed by a towing Vehicle, a double acting ram and cylinder arrangement, one part of which is operatively connected to one of the vehicles and the other part operatively connected .i

to the other Vehicle, a source of rfluid supply, an fautomatio inlet valve for each side of the arrangement, an outlet valve for each side of the arrangement, operator operated means controlling the. outlet Valves so that as one opens the other closes', the arrangement thus permitting the two parts of the arrangement to move rela-v tively in one direction or the other by opening one of the outlet valves and being prevented from reversing until the other outlet valve is opened whereby relative movement between the vehicles is selectively permitted in one direction or the other, an hydraulic brake transmission system comprising a second ram and cylinder arrangement one part rof which is operatively connected to the towed vehicle and the other part to that part of the first ram and cylinder arrangement which is operatively connected to the other vehicle, whereby the selective relative movement between the two parts of the rst ram and cylinder aoiaoas arrangement is transmitted to the two parts of the second ram and cylinder arrangement, an

hydraulically actuated brake operating mechanism for operating the brakes on the -towed ve-l hicle, and a conduit connecting the cylinder of the second ram and cylinder to the said mechanism, whereby the relative movement in one dlrection causes brake release operation and in the other direction causes brake application, an energy storing device which is loaded by the relative movement causing brake release and in unloading assists the brake application operation.

l0. In brake operating means ior use on a vehicle towed by a towing vehicle, a source oi liquid supply, a double acting hydraulic check device taking its supply from the source and one part of which is connected to one oi the vehicles and the other part to the other vehicle, the device operating to prevent relative movement in either direction between the vehicles, operator operated valve means for permitting discharge oi liquid selectively trom one side or the other oi' the device so as to permit relative movement Ain one dirction or the other between the two parts oi the device and hence between the two vehicles, hydraulically actuated brake operating means operating brakes on the towed vehicle anian hydraulic transmission system operated by the relative movement to cause the operation of the brake operating means, and a connection between the device and the system whereby liquidl discharged from one side of the device is ied to the system, the relative movement in one direction causing brake release operation and in the other direction causing bralre application operation.

1l. in brake operating means for use on a vehicle towed by a towing vehicle, a double acting ram and cylinder arrangement one part oi which is operatively connected to one oi' the vehicles and the other part operatively connected to the other vehicle, a source of liquid supply, an automatic inlet valve for each side oi the arrangement, an outlet valve for each side oi the arrangement, operator operated means controlling the outlet valves so that as one opens the other closes, the arrangement thus permitting the two parts of the arrangement to move relatively in one direction or the other by opening one of the outlet valves and being prevented from reversing until the other outlet valve. is opened whereby relative movemer between the vehicles is selectively permitted in one direction or the other, an hydraulic brake transmission system comprising a second ram and cylinder arrangement one part of which is operatively connected to the towed vehicle and the other part to that part of the rst ram and cylinder arrangement which isoperatively connected to the other vehicle whereby the selective relative movement between the two parts of the rst ram and cylinder arrangement is transmitted to the two parts of the second ram and cylinder arrangement, an hydraulically actuated brake operating mechanism for operating the brakes on the towed vehicle, and a conduit connecting the cylinder of the second ram and cylinder to the said mechanism, a second conduit between one side of .the cylinder of the lrst ram and cylinder arrangement and the hydraulic system whereby liquid discharged through one of the outlet valves is fed to the system and the relative movement in one direction' between the second ram and cylinder transmits through the liquid brake application pressure. to the braise operating means while relative movement in'the other direction effects brake release operation.

l2. The combination with the arrangement claimed' in claim, ll oi valve means which operates to limit the pressure at -which liquid is fed to the system and which operates to vprevent the reversal of how of liquid when the pressure in the system rises above that of the discharge liquid.

. i3. The combination with the arrangement claimed in claim ll of an energy storing device which is loaded bythe relative movement causing brake release and in unloading assists the brake application operation.

it. An arrangement as claimed in claim 9 and in which the second ram and cylinder are of an,-

nular form and the second ram is mounted on a draw bar extension of the hrst ram.

l5. .an arrangement as claimed in claim 9 and in which the operator operated means comprises an electrically operable device and in which there is provided an operator operated switch controlling the circuit of the device.

- i6. An arrangement as claimed in claim 9 and in whichv the two outlet valves are formed by a single double acting valve in operative connection and in which there is provided an operator operated switch controlling the circuit oi the device.

ll'. lin brake operating means for use on a vehicle towed by a towing vehicle, an hydraulic double acting check device for preventing relative movement between thextwo vehicles, operal tor operated means `controlling the discharge of liquid from the checlr device to enable` relative movement in one direction or the other `to be edected, an hydraulic braise operating system utilizing the relative movement to edect release or application ot braheson the towed vehicle and means whereby liquid'discharged trom .the

checir device to permit brahe application move-v ment is lied to the hydraulic syst/em there to transmit brahe application pressure.

CECIUL VANDEP M 

